The primary health concerns about LSD use are related to psychological health rather than risk of physical damage to the body or brain. As senior LSD researcher Dr. David Nichols, Distinguished Chair of Pharmacology at Purdue University and head of one of the world's top LSD research labs, stated in his 2004 review article on hallucinogens, "There is no evidence that any of the hallucinogens, even the very powerful semisynthetic LSD, causes damage to any human body organ. [...] Hallucinogens do not cause life-threatening changes in cardiovascular, renal, or hepatic function because they have little or no affinity for the biological receptors and targets that mediate vital vegetative functions."1 Deaths resulting from the pharmacological effects of LSD are rare to non-existent.

However, like all psychoactive drugs, LSD can induce cognitive and emotional alterations that can greatly affect behavior. With psychedelics such as LSD, there can be powerful and unexpected changes in thinking and perception. While under the influence of these drugs, an individual can exhibit poor judgement and delusional behavior, leading to accidents or dangerous situations. In those individuals predisposed toward certain psychiatric conditions, hallucinogens may precipitate psychotic responses or depression. In some individuals, long-lasting anxiety and/or depression may result from the unpleasant experiences and frightening visions that occurred during the psychedelic experience.

Experienced users often caution new users of psychedelics about the dangers of inebriated behavior and a common fear while inebriated that the effects of the drug will be permanent. One bit of popular trip wisdom highlights some risks of LSD use: "Cars are real. Cliffs are real. Cops are real. You cannot fly. It's never a good time to die. And don't forget: you will eventually come down." Sober sitters or psychotherapeutic guides are often suggested as a means of substantially reducing the risk related to adverse mental and physical events that may be associated with LSD use. Individuals have also been encouraged to prepare themselves psychologically for the experience, by being ready to accept whatever emerges out of their psyche ("I love this, too... even the snarling spider about to eat me who looks like my mother.").

LSD is reported to have some beneficial effects on health, including improvements in mental health; increased connection to spirituality; insights into self and world; the treatment of cluster headaches; use in combating addiction to other drugs and behaviors; and reducing use of pain medications and anxiety levels in people facing terminal illnesses. Although small-scale clinical studies by legitimate scientific laboratories have suggested these claims may be worthy of further investigation, large-scale clinical studies have yet to be conducted to validate this pilot work.

Less than a handful of deaths have been directly attributed in the medical literature to the pharmacological effects of LSD, and none of these have been unquestionably attributable to LSD's actions. Estimates of what could be a potentially lethal dose of LSD are higher than 10 mg orally, a dose that is more than 100 times the common, moderate dose of LSD (100 ug). The administration of this amount would require the ingestion of more than 200 units of street blotter, which typically contain about 50 ug of LSD (as of late 2010).

It is important to note that LSD has been associated with deaths as a result of inebriated behavior (falling from a height or fighting with police) or by suicide. There are also occasional deaths misattributed to LSD when another substance was actually taken.2

Precipitation of Psychosis.
LSD may have the ability to trigger psychotic symptoms in those predisposed to psychosis. This is problematic because psychotic or schizophrenic disorders most frequently manifest in those in their late teens or early twenties, the same age that use of LSD is most common. Individuals with a family history of schizophrenia or early onset mental illness should be extremely careful because LSD is known to trigger latent psychological problems. "Fortunately, however, these drugs do not appear to produce illness de novo in otherwise emotionally healthy persons, but these problems seem to be precipitated in predisposed individuals."1 This adverse event is apparently quite rare: as Dr. Nichols of Purdue University observed in 2004: "A search of Medline in early 2003 for case reports of LSD-induced psychosis found only three reports in the previous 20 years."1

Precipitation of Depression.
Experts dispute whether LSD use has been solidly linked to depression resulting in intentional suicide. See LSD Death: Suicide. LSD use, even in the context of formal psychotherapy, has been reported to trigger short-term or lasting depressions in some people.14 LSD psychotherapy researchers in the 1950s and 1960s regularly identified depression following an LSD experience in articles discussing its use. Betty Eisner and Sidney Cohen wrote: "We have observed that a transient depression sometimes follows an LSD-25 session. This may be due to several factors: (1) the inability to integrate all of the unacceptable traumatic material uncovered during the session; (2) the feeling that the necessary effort is too great to be undertaken; (3) "coming back to earth" after a transcendent experience. It is therefore important that some sympathetic person be with the patient during the evening following treatment. A more serious type of depression has been observed to occur when insights acquired under the drug are not translated into the life situation."14 People prone to depression or suicidal thinking may be more likely to suffer this response following exposure to psychedelics.

Dangerous Interaction: Lithium or tricyclic antidepressants.
LSD can cause dangerous reactions when used by someone taking lithium or tricyclic antidepressants. Some people report having experienced seizures after ingesting these combinations. Individuals have typically reported an undesirable intensification of the hallucinogenic response that is not akin to "getting higher for free". Such people have reported being unable to communicate with their friends, becoming uncharacteristically violent or going into fugue states (ending up somewhere else without knowing how they got there). In addition, the interaction of lithium and LSD has been reported by some persons to result in seizures in those who do not have a history of this condition. 3,4

Reduction of Response to LSD when taken with SSRI and possibly MAOI drugs.
In persons regularly taking selective serotonin reuptake inhibitors (SSRI) or monoamine oxidase inhibitors (MAOI) a reduction or abolishment of response to LSD has been reported. This effect is not reversible by taking a higher dose of LSD or by going off the antidepressant for a day or two. It generally appears to take weeks or a month off of an SSRI or MAOI before the full psychedelic response returns. However, it is not advisable to stop taking an antidepressant that is effective just to have an LSD experience.20 As opposed to the diminished effect resulting from chronic use, there have been some reports that the accute use of a MAOI in combination with LSD increases the psychoactive effects; this could be viewed as a sort of ayahuasca-like effect.

HPPD.
Hallucinogen Persisting Perceptual Disorder (HPPD) has been reported by individuals who have taken LSD. Although a large portion of LSD users report lasting visual effects, only a small percent of those report these effects as troubling. When lasting visual effects interfere with normal function, these are classified as HPPD, a disorder identified in the Diagnostic and Statistical Manual (DSM-IV-R). See the HPPD Vault.

Dramatic Changes in Thinking.
Changes to thought processes, while among the many reasons why people choose to use LSD, can also impair judgement. A sober sitter who assumes responsibility for the welfare of a person under the influence of LSD can reduce the chances of problems caused by impaired judgement. Some LSD-related deaths and injuries have been the result of dangerous behavior such as walking on a freeway, staring at the sun, stepping through a window, or fighting with police. [see Behavioral Fatalities]

Hyperthermia/Overheating.
While uncommon, a few cases have been reported in the medical literature of dangerous overheating following ingestion of LSD, including one non-fatal case that brought the patient's body temperature to over 106°F (41°C).6

Anxiety/Panic Reactions.
LSD may precipitate awareness of and access to surreal, existential, disorienting, or abstract psychological material resulting in experiences that are difficult to process, horrifically frightening, disturbing, or simply unsettling. These experiences and "insights" may result in lasting confusion about the nature of reality and the solidity of the material world. Individuals in the midst of emotional or psychological upheaval, due to personal history or stress in their everyday lives, are likely to be more prone to such reactions.

Pregnancy.
LSD and other closely related chemicals are known to cause uterine contractions, which may be problematic during a pregnancy. In the mid-20th century, there were many erroneous rumors about the possibility of chromosome damage resulting from the use of LSD during pregnancy. Further research has disproven this theory.10, 13

Breastfeeding.
LSD is likely to pass into breast milk although little data is available about how much or for how long. Recommendations range from waiting 24 to 120 hours after LSD use before resuming breastfeeding.7

No Potential for Physical Dependence (Addiction).
LSD does not cause physical dependence (as determined by the development of a withdrawal syndrome upon drug discontinuation following long-term administration). It is also not likely to lead to psychological dependence in most people, although there are a few reports of individuals who have taken it daily for months. As with most substances, a few people have reported developing a bad relationship with LSD, where they continue to use the drug despite adverse consequences in their lives. Tolerance (a reduction in response after taking the same dose of a drug on a subsequent occasion) begins with a single dose of LSD, due to a reduction ("down-regulation") of serotonin 5HT2 receptors. This effect is increased following continued use of LSD the next day, but reverses over time. Thus, using LSD two days in a row is likely to lead to a diminished experience the second day, but this effect is less likely if LSD is taken with at least three days in between experiences.

Positive Effect on Mood and Life.
Most users of LSD report that it has had a positive effect on their life, from simple recreational fun to profound life-changing spiritual experiences. In a survey conducted by Erowid on our website with over 49,000 valid responses, 53.4% of respondents reported that LSD use had affected their lives positively and only 3.4% reported it had a negative effect on their lives. The balance was made up mostly of 21.9% who reported that LSD had "no effect" on their lives over the long term and 17.2% who reported a "mix of positive and negative effects".15

Insights into Self, Other, and World.
Perhaps the most commonly reported benefits from LSD are changed perspective and substantive insights into one's life.16

Treatment of Cluster Headaches.
User reports by people with a severe form of migraine-like headaches called cluster headaches include descriptions of nearly complete blocking of the painful experiences with the use of LSD, psilocybin, and related compounds. Research into this issue is ongoing.8, 17

Use in Addiction Treatment.
LSD and other psychedelics have been investigated as an adjunct to psychotherapeutic treatment of addiction and alcoholism. Such research stalled in the late 1960s, when prohibition made studies with LSD much more difficult to conduct, and addiction treatment remains an unproven-yet-potential health benefit from LSD.18,21

Reducing End-of-Life Anxiety.
LSD and other psychedelics (such as DPT and psilocybin) have been shown to reduce depression, anxiety, and medication needs in some people facing terminal illness. 19